An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < K c Kep key kin Kra > >>

Number of Results: 88
Kramers' law
  قانون ِ کرامرز   
qânun-e Kramers (#)

Fr.: loi de Kramers   

An approximate expression for deriving the → opacity that depends upon temperature with a power law: κ ∝ ρT-3.5, where ρ represents the density. In → partial ionization zones, a part of the energy released during a layer's compression can be used for further ionization, rather than raising the temperature of the gas. As the temperature of the compressed layer has not substantially increased, the increase in density produces a corresponding increase in the opacity of the layer. Likewise, during the expansion phase, the temperature does not decrease significantly since the ions release energy when they recombine with electrons.

Derived in 1923 by the Dutch physicist Henrik Kramers (1894-1952); → law.

Kramers' opacity law
  قانون ِ کدری ِ کرامرز   
qânun-e kederi-ye Kramers (#)

Fr.: loi de l'opacité de Kramers   

Same as → Kramers' law.

Named after Henrik Kramers (1894-1952); → law.

Kronecker delta
  دلتای ِ کرونکر   
deltâ-ye Kronecker (#)

Fr.: delta de Kronecker   

The function δik of two variables i and j defined by δik = 1 if i = j, and δik = 0 if i ≠ j.

Leopold Kronecker (1823-1891), a German mathematician; delta, Gk. letter of alphabet.

Kruskal diagram
  نمودار ِ کروسکال   
nemudâr-e Kruskal

Fr.: diagramme de Kruskal   

A diagram used to plot trajectories in → space-time near a → black hole. The vertical and horizontal axes are two complicated functions of time and distance from the black hole. Lines of constant time radiate from the origin of the diagram, with steeper slopes corresponding to later times. Lines of constant distance are hyperbolas, lines of constant time pass through the origin; photons always travel along diagonal lines at ±45° to the vertical. The trajectory of an object falling into the black hole is shown as a curving line moving upward on the diagram at less than 45° to the vertical.

Named after the American physicist Martin David Kruskal (1925-2006); → diagram.

kripton (#)

Fr.: krypton   

A colorless, odorless, highly un-reactive gaseous chemical element and a member of the inert gas family. Symbol Kr; atomic number 36; atomic weight 83.80; melting point -156.6°C; boiling point -152.3°C.

Krypton, from Gk. kryptos "concealed, hidden". It was discovered in liquefied atmospheric air by the Scottish chemist William Ramsay and the English chemist Morris William Travers in 1898.

Kuiper belt
  کمربند ِ کویپر   
kamarband-e Kuiper (#)

Fr.: ceinture de Kuiper   

A region of the → Solar System extending roughly from the orbit of → Neptune, or 30 → astronomical units (AU), to 50 AU from the Sun that contains many small icy bodies. The Kuiper belt is now considered to be the source of the → short-period comets.

Named after Gerard Peter Kuiper (1905-1973), a Dutch-born American astronomer, who predicted the belt in 1951. He is also considered the father of modern planetary science for his contributions to the study of our solar system; → belt.

Kuiper belt object (KBO)
  بر‌آخت ِ کمربند ِ کویپر   
barâxt-e kamarband-e Kuiper

Fr.: objet de la ceinture de Kuiper   

A → Solar System object belonging to the → Kuiper belt. The largest known objects of this type are → Pluto and its moon → Charon, → Quaoar, → Sedna, and → Orcus. See also → trans-Neptunian object.

Kuiper belt; → object.

afrâštegi (#)

Fr.: aplatissement   

The measure of "peakedness" of the curve describing a frequency distribution in the region about its mode. The kurtosis of the normal distribution is 0.

From Gk. kurtosis "bulging, curvature," from kurtos "convex," kirkos "a ring;" cf. Av. skarəna- "round;" L. circus "circle, ring;" PIE base *sker- "to turn, bend."

Afrâštegi condition, state adj. of afrâšté "elevated, erect, upright," p.p. of afrâštan "to raise, exalt, extole," from Mid.Pers. abrâstan, abrâz- "to lift, raise," from ab-, from O.Pers./Av. abiy-/aiwi- "to, upon, against;" cf. Skt. abhi-, Gk. amphi- + râst "straight, direct, true;" from O.Pers. rāsta- "straight, true," rās- "to be right, straight, true;" Av. rāz- "to direct, put in line, set," razan- "order;" cf. Skt. raj- "to direct, stretch," rjuyant- "walking straight;" Gk. orektos "stretched out;" L. regere "to lead straight, guide, rule," p.p. rectus "right, straight;" Ger. recht; E. right; PIE base *reg- "move in a straight line," hence, "to direct, rule."

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